Method for deinking printed paper



Patented May 18, 1926.

UNITED STATES 'LADISLAUS EMANUEL GRANTON, or LoNDoN, ENGLAND.

METHOD FOR DEINKING PRINTEDPAPER.

N'o Drawing.

This invention relates to improvements in the removal of printers inkfrom papers and withthis object in view such papers in accordance 'withthis invention are pulped or shredded in the presence of aqueoussolutions containing one or more alkalis or alkaline reactingsubstances, then agitated in the presence of artificially colloidized orpartially colloidized mineral substances and finally Washed and furthertreated. in .well

known manner.

For the purposes of this invention the mineral substances are thosehaving detergent properties such as the silicates of magnesium forexample, soapstone, talc etc; clays such as china clay or kaolin;fullers bakrth, kieselguhr etc., or silica. powder or the Such mineralsubstances are brought into 2 a colloidized or partially colloidizedstate by known grinding or agitating means for instance, as .intimatelyas possible in the presence of a relatively small quantity of a solutionof what may be called a dispersator or deflocculant but which perhaps inthis case is better termed a protective colloid having adhesiveproperties, such as casein, gelatine in its various forms, gluesalbumens, gums such as gumarabic -or gum tragacanth,

' starch, dextrin or the like, alone or admixed.

The efiect of such small quantities of protective colloids is difficultto explain but their presence certainly leads not only to a better'colloidization of the mineral substances but 5 also to enhanced andmore rapid de-inking or decolouring results when such mineral substancesare brought into intimate contact with the paper than has hitherto beenthe case.

The following example serves to illustrate the materials and quantitiesthereof that have been used successfully for carrying the invention intoeffect. The heating apparatus employed was of ordinary known type.

About 450 grammes of ground soapstone are added to and mixed with about4.300 grammes of water. After adding a semisolution of 9 grammes ofcasein inalkaline water, the whole mixture is intimately ground forabout 10 minutes, the time depending upon the construction of thegrinder or disintegrator. To about 24 to 26 kilogrammes of printed paperwhich is being ulped in a beater containing about 475 to 480 kilogrammesof water and approxi- Application filed March 26, 1924. Serial No.702,151.

mately 120 grammes of caustic soda or its equivalent in washing soda orsimilar alkali, the above described mixture is added and the agitationis continued for about 20 or 30 minutes until the printers ink has beenremoved from the finely pulped paper.

The liquor containingthe ink in suspension is then removed from the pulpby washing in drum washers or other washing machines as known in theart'.

After the aforesaid treatment any remaining traces of alkali may ifnecessary be removed or neutralized with acids or acid salts in the wayknown in the paper trade and the pulp is, after bleaching or colouring,or both, in known manner, made into paper which is again quite suitablefor printing or other purposes.

While the invention is primarily intended to be used for printed whitepaper the process has also been successfully employed with several kindsof coloured papers.

Experiments have shown that equally good de-inking results can beobtained with fullers earth and gelatine, and that satisfactory resultsare given with kieselguhr and glue; china clay and dextrin or albumen;silica powder and starch solution; asbestos powder and gum arabic; etc.,all of said substances being used in substantially the same proportionsas those given above for soapstone and casein.

I am aware that the use of alkalis or alkaline substances for looseningthe ink from the paper is known and also that a treatment for thede-inking of paper with peroxides of alkalis or alkaline earth metalsand colloidal compounds such as colloidal silicic acid has already beenproposed. Furthermore that the use of natural clays having the physicaland chemical properties of Bentonite in combination with alkalis oralkaline reacting substances has been suggested for the same purpose,and I make no claim to the use of such natural clays per se but What Iclaim is i 1. A process for de-inking prlnted paper comprising the stepsof pulping the-paper 1n the presence ter; then subjecting the pulp,under agitation, to treatment with an aqueous composition, made bycausing a mineral substance having detergent properties to become asfinely sub-divided as possible in water with 1 of a solution of alkalinecharacthe aid of an organic protective colloid hav-.

' ing adhesive properties; and finally washing comprising the steps ofpulping the paper in the presence of a solution of alkaline character;then subjecting the pulp, under agltation, to treatment with an aqueouscompositron, made by causing a mineral silicate having detergentproperties to become as finely sub-divided as possible in water with theaid of an organic protective colloid having adhesive properties; andfinally washing the ulp. P 3. A process for de-inking printed papercomprising the steps of pulping the paper in the presence of a solutioncontaining caustic alkali; then subjecting the pulp, under agitation, totreatment with an aqueous composition, made by causing soapstone tobecome as finely sub-divided as possible in water containing casein insolution; and

:finally washing the pulp.

4. A process for the removal of printers ink from paper, comprising thesteps ofpulping the paper; and then mixing the pulp with an aqueouscomposition containing a finely-divided mineral silicate and casein.

5. A process for the removal of printers 30 ink from paper, comprisingthe steps of pulping the paper; and then mixing the pulp with an aqueouscomposition containing finely-divided soapstone and casein.

6. A process for the removal of printers ink'from paper, comprising thesteps of pulping the paper; mixing ground soapstone with water; addingthereto a semisolution of casein; grinding the resultant mixture; mixingthe paper pulp and ground mixture to ether; agitating the final mixture;and then subjecting said final mixture to washing.

7. A process for the removal of printers ink from paper, comprising thesteps of 4 pulping the paper; rinding a detergent mineral substance in te presence of an organic protective colloid having adhesive propert1es;mixing the paper pulp and ground mixture together; agitating the final50 mixture; and then subjecting said final mixture to washing.

In testimony whereof I afiix my signature.

LADISLAUS E. GRANTON.

